ITU-T Recommendation G.651.1 recommends a quartz multimode fibre to be used for the access network in specific environments. These environments are multi-tenant building sub-networks in which broadband services have to be delivered to individual apartments. The recommended multimode fibre supports the cost-effective use of 1 Gbit/s Ethernet systems over link lengths up to 550 m, usually based upon the use of 850 nm transceivers. The recommended fibre type is an improved version of the well-known 50/125 µm multimode graded-index fibre as recommended in ITU-T Recommendation G.651. Its cost effective use is very common in datacom systems applied in enterprise buildings throughout the world for quite a number of years.